A turbine, for example a gas or steam turbine, typically includes a turbine casing with a rotor journaled for rotation therein. A number of turbine blades can be mounted on the rotor. The turbine casing typically includes curved inner surfaces adjacent the periphery of the turbine blades, called rows. Occasionally the rows may require machining as part of a repair or refurbishment operation. Three different types of cuts may be required to completely machine each row. A radial cut, a longitudinal cut (sometimes called a turning cut), and a hook, or face grooving (sometimes called trepanning).
Currently, to gain access to the surface of the rows to be machined requires removing the top portion of the turbine casing, then removing the rotor. Removing the rotor from the turbine casing can be difficult. Further, the top portion of the casing may splay slightly when uncoupled to the lower portion of the casing, which in turn requires a special asymmetrical machining operation to machine the rows in the top portion.